Method of making articles composed of resistance material



1963 JLCFZENOBIA, JR 3,100,331

METHOD OF MAKING ARTICLES COMPOSED OF RESISTANCE MATERIAL Filed Feb. 1, 1960 TORNEY United StatesPatent O METHQD F MAKHNQ ARTICLES CUMPGSED 0F RESISTANCE MATERIAL John C. Zenobia, in, Eelleville, Ni, assignor to Specialties Development (Iorporation, Belleville, N01, a corporation of New Jersey Filed Feb. 1, 1960, Ser- No. 5,750

4 Claims; (Cl. 2 9--155.71)

The present invention relates to an improved method.

of making electrical resistors such as thermistors, varistors and the like,which essentially consist of a bead-like body composed of resistance materiaL-thermally and/ or voltage sensitive resistance materials such as metallic oxides and at least two terminal wires.

Heretofore, it hasbeen proposed to make such eleportions of the terminal wires to make a-reliable'electrical connection, particularly in networks wherein the elements are subjected to low voltages, such as one volt for example. The proper cleaning ofthe'wires is extremely difiicult and often results indamage to the bodies I Accordingly, an object of the present invention is'to provide a method of making such elements which eliminates the necessity of cleaning the terminal wires.

Another object is to provide such a method which is simple, practical and economically feasible.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled inthe art upon; employment of the invention in practice.

In accordance with the present invention, the forego-' ing objects are generally accomplished by making the elements from a' string of bead-like bodies of resistance material extruded onto spacedapart parallel wires b-y stretching the wires to reduce the diameter thereof along their length to thereby release the bodies therefrom, sliding the bodies past theends of the wires to remove the bodies therefrom, inserting terminal wires into the holes of each body formed by the wires from which the bodies have been removed, the terminal wires having substantially the same diameter as the first mentioned wires before reduction in diameter, and firing the bodies to adhere the same onto the terminal wires.

3,100,301 Patented Aug. 13, 1063 Referring to FIG. 1 of the drawing in detail, there is shown a portion of a continuous length of an assembly which comprises a pair of parallel spaced apart, electrically conductive wires 10 and 11, and a mass of resistance material which has been extruded onto the Wires and has been notched at lengthwise spaced apart points 12 to form a series of bead-like bodies 14 at least partially connected at 15.

The extruded material is in the state of a stiif'plastic mass which adheres to the Wires as shown in FIG. 2. Preferably, the material is air dried at least partially to remove moisture and cause the bodies to be hardened sufli'ciently to retain their shape. and remain adhered onto the wires to thereby facilitate further handling of the assembly.

As a specific example, the mass may be composed essentially of a mixture of about 90% manganese dioxide and about 10% cupric oxide acting as the resistance material, although numerous other known resistor, thermistor or varistor compositions may be employed in practicing the invention. In order to-render the mass extrudable and shrinkable when fired andto fuse orbond the mass onto the wires, the resistance material admixed with a frit, steatite and flour or the like, and a sufficient amount of water is added to make the resulting mass plastic by following the teachings known in the art as' exemplified by U.S. Patents 2,495,867, 2,785,142, 2,856,368 and 2,871,197.

The bodies and the wires may have the following dimensions:

. In. Body length 0.0625 Body diameter 0.0 625 Wire diameter 0.0100 Space between wires 0.0100

The wires may be made of an alloy sold under the trademark Nichrome by Driver Harris Co. and consisting essentially of between about 80% and about 85% by A preferred embodiment of the invention has been chosen for purposes'of illustration anddescription, and is shown in the accompanying drawing, forming apart of the specification wherein:

FIG. 1 is a'fragmentary elevational view of an asstring of bead-like bodies extruded onto of the wirereduced to release the bodies and the bodies separated; 7 FIG. 4 is a greatly enlarged longitudinal sectional view of one body adhered to terminal wires.

weight of nickel and between about 20% and about 15% by weight of chromium; or may be made from an alloy and sold under the trademark Inconel by The In ternational Nickel Company, Inc. and consisting essentially of between about 6% and about 18% by weight of iron, between about 11% and about 18% by weight of chromium and the balance nickel at a minimum of by weight. It is apparent that other non-precious metal containing alloys can be employed in practicing the invention.

In FIG. 3, two bodies 14 are shown with the wires 10 and 11 stretched along their length beyond their elastic limit to reduce their diameter sufiiciently to release the bodies. This can be accomplished by a reduction in diameter between about 10% and about 20%. For example a wire having a diameter of 0.010 in. may be reduced to 0.008 or 0.009 in. and a wire having a diameterof 0.008 in. may be reduced to 0.007 in.

After the bodies are released, they are disconnected by by breaking the connection15 and are stripped from the wires by sliding them past the ends of the wires to produce separated bodies. Alternatively, any desired number of bodies could be allowed to remain connected to produce elements having more than one body, or a number'of connected bodies could be first stripped from the wires and then disconnected fromeach other as individual bodies or groups of bodies. Thus, the term bead-like body means, a body having one or more bead sections.

The bodies will haveholes 16 therein which correspond to the initial diameter of the wires Ill-and 11 before reduction in diameter theerof.

As shown in FIG. 4, terminal wires 17 and 18 are inserted into the holes 16, and the body 14 is fired at a temperature to shnink the same and cause it to be permanently bonded to the terminal wires.

Preferably, the terminal wires are of the same material and have the same diameter as the wires and 11, and in actual practice the wires 10, 11, 17 and 18 are from the same source of supply. This assures that the wires 17 and 18 fit snugly in the holes 16 and that the body 14, upon firing, is bonded thereto.

In order to facilitate insertion of the terminal Wires, the ends 19 thereof may be tapered.

' From foregoing description, it will be seen that the present invention provides a simple, practical and reliable method of making electrical resistors which have clean terminal Wires without resorting to the use of platinum wires whereby the expense of producing such elements is materially reduced.

It will be understood that the .details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

I claim:

l. The method of making electrical resistors having a resistance value responsive to a condition from a string of bead-like bodies partially connected to each other and formed of a heat shrinkable and bondable composition including resistance material, the bodies being extruded onto spaced apart parallel ductile metallic Wires and being in at least a partially dried and hardened state and adhered to the Wires, which method comprises stretching the wires to reduce'the diameter thereof along their length to thereby release the bodies therefrom, disconnecting at least certain of adjacent bodies from each other and slidingthe bodies past the ends of the wires to remove the bodies therefrom, separating the disconnected'bodies, inserting terminal wires into the holes of each body formed by the wires from which the bodies have been removed, the terminal wires having substantially the same diameter as. the first mentioned wires before reduction in diameter, and firing the bodies to shrink and bond the same onto the terminal wires, said method steps being carried out in the sequence set forth herein. v

2. The method of making electrical resistors having a resistance value responsive to a condition from a string of bead-like bodies partially connected to each other and 'formed of a heat shrinkable and bondable composition including resistance material, the bodies being extruded onto spaced apart parallel ductile metallic wires, which v 4 j have been removed, the terminal wires having substantially the same diameter as the first mentioned Wires before reduction in diameter, and firing the bodies to shrink and bond the same onto the terminal Wires, said method steps being carried out in t-he sequence set forth herein.

3. The method of making electrical resistors having a resistance value responsive to a condition from a string of bead-like bodies partially connected to each other and formed of a heat shrinkable and bendable composition including resistance material, the bodies being extruded sliding the bodies past the ends of the wires to remove.

the bodies therefrom, separating the disconnected bodies, inserting terminal Wires into the holes of each body formed by the wires from which the bodies have been removed, the terminal wires having substantially the same diameter as the first mentionedwires before reduction in diameter, and firing the bodies to shrink and bond the same onto the terminal wires, said method steps being carried out in the sequence set forth herein.

4. The method of making electrical resistors having a resistance value responsive to a condition from a string of bead-like bodies partially connected to each other and formed of aheat shrinkable and bondablecomposition including resistance material, the bodies being extruded onto spaced apart parallel ductile metallic wires and being in at least a partially, dried and hardened state and adhered to the wires, which method comprises stretching the wires to reduce the diameter thereof along their length between about 10% and about 20% to thereby release the bodies therefrom, disconnecting'at least certain of the bodies, sliding adjacent bodies from each other past the ends of the wires to remove the bodies therefrom, separating the disconnected bodies, inserting terminal wires into the holes of each body formedby the wires from which the bodies have been removed, the

terminal wires having substantially the same diameter as the first mentioned Wires before reduction in diameter, and firing the bodies to shrink and bond the sameonto the terminal wires, said method steps being'carried out.

method comprises at least partially drying the bodies to harden the bodies and to adhere the bodies onto the Wires, stretching the. Wires to reduce the diameter thereof along their length to thereby release thebodies therefrom, disconnecting at least certain of adjacent bodies from each other and sliding the bodies past the ends of the wires to remove the bodies therefrom, separating the disconnected bodies, inserting terminal wires into the holes of each body formed by the wires from which the'bodies in the sequence set forth herein.

References Cited in the file of this patent UNITED STATES PATENTS 2,199,879 Deroche May7,j1 940 I 2,271,774 Megow et al. 'Feb. 3, 1942 2,566,335 Ioerren Sept. 4,-1'951 2,664,486 Colpitts Dec. 29; 1953 2,937,354

Mazza-rella et al May 17, 19

. m -56. as- 

1. THE METHOD OF MAKING ELECTRICAL RESISTORS HAVING A RESISTANCE VALUE RESPONSIVE TO A CONDITION FROM A STRING OF BEAD-LIKE BODIES PARTIALLY CONNECTED TO EACH OTHER AND FORMED OF A HEAT SHRINKABLE AND BONDABLE COMPOSITION INCLUDING RESISTANCE MATERIAL, THE BODIES BEING EXTRUDED ONTO SPACED APART PARALLEL DUCTILE METALLIC WIRES AND BEING IN AT LEAST A PARTIALLY DRIED AND HARDENED STATE AND ADHERED TO THE WIRES, WHICH METHOD COMPRISES STRETCHING THE WIRES TO REDUCE THE DIAMETER THEREOF ALONG THEIR LENGTH TO THEREBY RELEASE THE BODIES THEREFROM, DISCONNECTING AT LEAST CERTAIN OF ADJACENT BODIES FROM EACH OTHER AND SLIDING THE BODIES PAST THE ENDS OF THE WIRES TO REMOVE THE BODIES THEREFROM, SEPARATING THE DISCON- 